Telephone system



y ,'l930.v T. F. CROCKER 1,771,842

. I v 'iPELEPHdNB SYSTEM Original Filed Sept. 26. 1927 2 Sheets-Sheet: 1

TOLL SERVICE TRUNK f rm Thurnas F Er u'ckgr T. F. CROCKER 1,771,842

TELEPHONE SYSTEM Original Filed Sept. 26. 1927 2 Sheets-Sheet 2 July 29,1930.

IfiiFfiffi I I 'Thmas F Crbclgar IIIIII NEQ control of the sleeveconductor of the cord, the

, Patented July 29, i 1930 UNiTEn STATES (PATENT OFFICEI THOMAS F.CROOKER, OF CHICAGO, ILLI NOIS,,ASSIGI\TOR TO RESERVE HOLDING COM- PANY,0F KANSASCITY, MISSOURI, CORPORATION OF DELAWARE TELEBHONE sYsTEMApplication filed September 26, 1927, Serial No. 221,878. -Renewed.December 12, 1929.

The present invention relatesto telephone systems ingeneral, but isconcerned more particularly with cord circuits and trunk circuits usedin giving toll service 'to the subscribers of an automatic telephoneexchange. I

' This invention is an improvement on my prior application Serial No.161,514, filed January 17, 1927, particularly with reference to thefeature in the'prior application involving the arrangement whereby thedialling keys and other keys are common to allthe cord circuits of anoperators position.

One object of the invention is the produc tion of suitable apparatuswhereby the amount of workperformed by the operator is reduced. This isaccomplished byremoving the cord-splitting contacts from the dial keysand placing them on suitably-controlled relays. Inthis way,'one or theother of the two dial keys may be left thrown all thetime, with theresult that the proper cord-splitting relay operates at the proper time.to cause the impulses from the operators dial to be transmitted over theend of her cord circuit indicated by which of the two dialling keys is.left operated. I v

In this connection, a saving of contacts and a simplificationof thecircuits result, because the same cord splitting relays above men tionedfor use in connection with dialling may be used to perform thecord-splittingoperation necessary during coin collect and refund andsuch other operations as may re' quire a splitting of the cord;

It is a further object to prevent the operator from hearing severeclicks. when she plugs into a trunk line withher talking key thrown,asshe may often do when she is inserting the calling plug of a cord intoa trunk line jackjafter she has answered a call with the answering plug.This object isobtained by providing a short-circuiting relay to shortcircuit the receiver of the operatorunder the arrangement-being suchthat the sleeve of the plug contacts with the sleeve of the jack andcauses her receiver to be short 'circuited before the tip and ringcontacts of the plug and jack have been brought together. I

A feature of the present arrangement in connection with the operatorsheadset is that the operators receiver is maintained short circuited byrelays controlled by off-normal contacts of the calling device for aninterval following the operation of the calling device in order topermit a'selector, operated by the train of impulses just sent out, tocomplete its hunting operation and switch through so as to avoiddisagreeable clicks in the operators receiver when the switching throughopsults in the closure of an alternate holding circuit during theringing operation, whereas the holding circuit is not closed by the sameaction of the sleeve relay during dial-. ling; I Another object of theinvention is the production of novel circuit arrangements in connectionwiththe operators cord circuit for timing a conversation and warning theoperator when the subscribers have conversed for a predetermined lengthof time, three min-- utes, for example. In the specific embodiment ofthe invention hereindisclosed and described, the/operator is providedwith a starting pushbutton (common to her several cord circuits) whichshe operates whenthe conversation begins. timed to operate at the end ofthe predetermined interval, operates to signal the operator at the endof such interval.

It is a further object of the invention to simplify the operatorscordlcircuitsbycaus ing the calling supervisory lamp to flash whenthecon'versation has proceeded for thepredetermined interval, ratherthan using a sep-' aratelamp.

There'are' other objects and features of a;

A slow-acting device,

invention, having to do for the most part with the circuit detailsinvolved in carrying out the foregoing.

The various objects and features of the invention will be understoodbest upon a further perusal of the description in connection with theaccompanying drawings, comprising Figs. 1 and 2, showing by means of theusual circuit diagrams so much of the apparatus in a telephone systemembodying the features of the invention as is necessary to anunderstanding of the same.

In the accompanying drawings, Fig. 1. showsa cord circuit at atoll-operators switehs board together with a jack-ending toll line atthe left and'a toll service trunk at the right. The toll line may be oneextending to a distant city. The toll service trunk is a trunk lineleading to a toll servicetrunking system such as, for example, the oneshown in the Wicks Patent #1,633,149, granted June Fig. 2 shows theposition equipment, common to all the cords of the switchboard,including the various keys and relays and the operators headset.

The invention having been described generally, a detailed description ofthe operation of the apparatus shown will now be given. For this purposeit will be assumed that the operator receives a call over the toll line,Fig. 1, for a subscriber Whose line terminates in the local exchange.

In response to the ringing current transmitted over the toll line fromthe distant end thereat line relay 101 is operated and closes a lockingcircuit for its lower winding through contacts of cut-off relay 102, atthe same time closing a circuit for the call lamp 103. The operator,upon noting the lighted condition of the call lamp, inserts theanswering plug of an idle cord circuit, for example the one shown in thedrawings, into the jack J 'VVhen the plug P enters the jack J, cut-offrelay 102 is energized through the sleeve of the plug and jack andremoves the line relay from in bridge of the talking conductors of theack, at the same time unlocking the line relay so as to extinguish thecall lamp 103.

The circuit of relay 1.02 at this time includes contacts'of the ringingkey, contacts of the talking key, contacts of relays 107- and. 106 andthe supervisory lamp 103 and resist ance 104 in parallel. The lamp 103however is not lighted owing to the relatively high resistance of relay102.

Having inserted the plug P into the jack J the operator operates hertalking key in the cordcircuit so as to be able to converse with thecalling operator. When the talking key is thrown, it connects the tipand ring conductors of the answering plug to the common conductors 131and 132 leading to the position equipment shown in Fig. 2, and itdisconnects the sleeve of the plug P from the associated equipment inthe cord circuit and extends it over conductor 133 to the holdingcircuitincluding resistance 202 Fig. 2, and contacts on certain of thecommon keys. The tip and. ring strands of the plug P having beenconnected over conductors 131 and 132 and through contacts of the cordsplitting relay 201 to the tip and ring conductors with the callingoperator and ascertainthe destination of the call. 4

As a further result of the operation of the talking key, relay 108, Fig.1, is operated and it divides the cord into two sections, connecting thetip and ring strands ofthe calling plug P over conductors 13 1 and 135to the position equipment shown in Fig. 2. Relay 108 also disconnectsthe sleeve of the plug P from the associated supervisory lamp 112 and,assuming the dial call key to be normal, connects it over conductor 136to the common holding resistance 203, Fig. 2, through contacts ofcertain of the common keys. However, if the operator has the dial callkey operated, andshe usually has, thev sleeve conductor 136 of thecommon apparatus is extended through contacts of thedial call key,contacts of the off-normal relay 209, associated with the calling deviceCD, and contacts of relay 205 to the upper winding of relay 207 forpurpose which will appear presently. a

Having ascertained the number of the dc sired subscriber, the operatorinserts the plug P of the cord circuit into the jack of an idletoll-service trunk, the jack J for 8X- ample. As the plug is insertedinto the ack, the tip of the plug makes contact with the tip of thejackbefore the ring of the plug makes contact with the ring of the ack,due to the usual plug and jack construction, whereupon the upper springcontacts of the jack are closed by the associated tip springs, groundingthe upper terminal of sleeve relay 115. This ground potential istransmitted through relay and the sleeve of the jack to the sleeve ofthe plug, causing the quick acting relay 207 Fig. 2 to'energize over thesleeve'circuit and through the contacts above mentioned, to shortcircuit the operators tele phone. It has been found by test that thisshort circuiting operation is completedbefore the ring contact of theplug makes contact with the ring spring of the jack, preventing a clickin the operators headset from the battery potential across the tip andring contacts of the jack;

Sleeve relay 115 of the trunk line energizes at this time and closes abridge across conductors l20'and 121through the lower winding of relay116 and the winding of relay 119. Relay 119 energizes through the linerelay (not shown) of the switch to which the toll-service trunk extends,but the electropolarized relay 116 does not operate at this l il trunk.Upon energizing, {relay119 closesa parallel holding. circuitacrossconductor's 120 an d 121 through. the resistance .118,: at thesame time removingsthershunt fromlaround the associated condensers..These condensers, 'itmaybe,pointedout, are otasufiicientcapacity. topermit ringing tonesand-busy. tones ,to be heard. bythe opera-tor, but.they? .pre vent the starting ofythe ringing operation in the tollservice trunkingl systems due to. stray ringing currents. Relay-3 1194remains operated byv currentLflowr throughiiittin multiple with theholding resistancefllS.

-. Referring now 1 to the ,operators headset sl1own.in'.-Eig; 2, as 31:further result of the above mentioned energization' ofrrelay207,overthe.sleeveycircuit of the. plug P Fig. 1,

acircuit is closed for-the. slowsacting-zrelay .206. Relay 206 thereuponoperatesandcloses a multiple shunt around'the:.operator?s-receiver invaddition, to closinga .circuititor. relay ,205 through 5 the ,resistance.208. FRelay 208 operates andlocksitseltto the sleeve extendedconductor, at the. same time joining the two terminals of the l lowerwinding of relays 1207. together ,and .openinggthe circuit throughltheupper winding of the relay. Relay 207, being quick to v pull ,upinitially, as above pointedout-,I is.-.now.."slo'w .to. .fall back dueto the closedlowerwin'ding. After an interval, relay 207'fallsLback. andopensthe circuit of -relay }206,..whereupon. relay206 falls back; a,moment ilaterandrremoves.the shunt from around the. operatons telephone,at the same time;openingthe initial circuit of the now-locked relay 205.E'Iheresistance 208 is included in ,the initiahoperating .circuit of therelay :205 so as to avoid shunting the sleeve relayf115Iin the ,to'llservice: trunk By the time the relays 205.'z2.07.have gone throughthe-above. cyfcle'ofoperation the cur rent flow inconductors.12O1an'dl21, Fig. ilg-has become steady and. the condensersassociated with relay v11.9. have beeninserted in the talking circuit sothatno. .clickzi's ;pro.duced when the shunt is removedfromaroundthe-opera-v torstel phone. I r

'Having inserted theplugfP rinto.thejack J 7 with 'theabovedescri'be'dresults, theoperator,

who, as above mentioned, is assumed ztoihave left'the dial .callfkey.Fig.2.operated. fromxthe previous operation, how'turnsi her callingdevice GDin 'accorfdance withthe various digits inthe desired number; i3

When the callingldeviee CDIis moved from its 2 normal; position, theyeti-normal springs 231, 232, and .233 all make. contact with eachother. the contact is made between isprin'gs 22321.2 and-F233, 1 acircuit is 7 closed through relay 209 and contactsof theopertorsrheadset conductors; When springs232 and 231 make contact, theground potential from'spring- 233 is extended to the upper winding: ofrelay 207 ,"whereupon relay 207 operates, followed by the operation ofrelay' "5206. With these two relays operated, the

operators telephone is short circuited, as is ated dial call keyhfor thecut-off relay 201, ':whereupon..relay 201 responds and d scon-p-:ne'cts' conductors131 and 132 from the opera ::associated condenser inthe talking circuits.

Relay- 209 operates 'inseries with, the'Ic'ut-oii relay'20l and openstheextended sleeve circuit, permitting the sleeve relay 115 in thetollservice trunk Fig. 1 to; fallback. Belay 205 2, remains operatedfdue to'the. circuit closed' for it through resistance 208' by relay .206. 1Whenrelay falls-back, it opens the circuit through the lower windingofre'lay 116 and the winding of relay 119, whereupon relay/119 fallsback 'and short circuits the associated condensers, at the same'tirnere- :rnovi ng the bridge includingresistance 118 rfrom across conductorsand 121. The

"current flow formerly existingthro'ugh these :two bridges now takesplace "over the tip and ring springs of the jack and the correspond-:ingcontacts ofthe plugthrough the extended 'tipfand ring"conductors'134 and 135 and through theoperators headset byway of con-.

'tacts 'on'cut-ofl? relay 204, the condenser associated with theoperators headset being short .cir'cuited'by 'contacts of the operatedrelay 206. I The path of thiscurrent flowit will be noted-is through theimpulse'springs of the calling device CD. i As the dial of the callingdevice rotates ba-cktoits normal position, 'afterhaving been released,the'circuit is interrupted the neces sary number of times'at the impulsesprings of the-calling. devicesoas to bring about the desired operationof the first switch in the toll/service traini I 'VVhen the callingdevice 'CD reaches its normal position, the cit-normal springs 231-233separates, whereupon relay 209 fallsback,

butthe slowacting relay201'remains operated "for aslight interval-so asto permit a more stable condition to be reestablished inlower windingofrelay 116. Relay 119 now energizes'iin multiple with the" loop' throughthe operatorsheadset and the calling device CD, .Fig. 2, and closes thelocal multiple bridge through resistance'118, at the same timereinserting the associated "condensers the calling device CD reaches itsnormal position, with the result that relay 207 falls back after aninterval, being rendered slowacting by the closed circuit throughitslower winding. llpon fallingiback, relay 207 opens the circuit of theslow acting relay 206, with the result that relay 206'falls1back afteraninterval and removes the shunt from around the associated condenser inthe talking circuit, at the same time opening the local locking circuitfor relay 20-3 andremoving the shunt from around the operatorstelephone. The circu'ithaving become stabilized in the meantime, with nocurrent-flow in the operators circuit, no click is heard. Relay 205remainslocked upxover the extended sleeve circuit. 1 V

The operator now dials the remaining'digits in the desired number.

If the called line is busy, the busy tone is heard by the operator afterthe complete number is dialled, and she-may release the connection bywithdrawing the plug P from the jack J Assumingthat the called lineisidle,"the connector in use seizes the called line and initiatesoperationswhich result in a reversal of the current fiowlin conductors120 and 121. This takes place after relays'115 and 119, of the trunkhave reoperated,but before the operators relays 207 and 206 have fallenback. When this reversal occurs, relay 116 operates as the current flowsin its windings now assist each other, and relay 119 falls backmomentarily owingto the fact that the magnetism in its magnetic circuitmust die down to zero and build up againin the opposite direction whenthe current flow is're; versed. If it were not, for the presence of thebridge including resistatnce 118 across the trunks through contacts ofrelay 119, the

' line relay supplying current. to conductors 120 and 121 would fallback .at this time due to the high impedance of relay 119. How ever,resistance 118 affords a ready path for the reversed current flow overwhichthe line relay is held until relay 119 lets go. VVhen relay 119lets go, the, associated condensers are short circuited and the currentflow over 1 conductors 120 and 121 is continued through the operatorscircuit (the condenser and the operators telephone being still shortcircuited by relay 206 Fig; 2).

through resistance 118 is picked up-again when relay 119 energizes inthe opposite di-f rection.

As a result of the energizationof the electro-polarized relay 116, aground-return holding circuitis iprepared'at the lower armature of therelay, and a shunt-is placed 7 stores the talking key.

The current flowaround the upper winding of sleeve relay 7 115 at theupper contacts of the electropolarized relay through contacts of relay119, thereby pe'rmittingan'increased current flow over the sleevecircuit so as to light the supervisory lamp 112 when the operator re-Having dialled thenumber and not having received the busy signal, theoperator new restores her-talking key, whereupon relay 108 falls backcompletely disassociating the cord circuitfrom the position equipment.The sleeve circuit of the plug P is now transferred back to thesupervisory lamp 112 whereupon the lamp 112 becomes lighted over thesleeve circuit in series with the lower winding of the sleeve relay115,the upper winding of-thisrelay being now shunted by the relays 116*and119. By the lighted condition of thelamp 112, the operator isinformed'that the called'line is idle and has been seized."

In order to signal the subscriber on the called line, after she has beennotified to do so by the calling operator, the operator throws theringing key associated with a plug P whereupon ringing current istransmitted over the tip and ring conductors of the jack J At the sametime, the shunt is removed from around the resistance 11 1 by theringing key, extinguishing the lamp 112 and causin the sleeve relay 115to fall back. The resistance 114 must not be sohigh as to cause thedeenergi'zati'on of a tool-line sleeve relay such as 102associated withthe jack J As 'a result, the resistance is high enough to cause thesleeve relay to fall back when its upper winding is shunted, but nototherwise. Theup'per' win'ding of the relay is shunted at this'time bythe contactslof relays 116 and 119. When the sleeve relay falls back, itgrounds the lower conductor 121 through contacts ofrelay 116, at thesame time opening the -bridge throughthe lower winding of relay'116 andrelay 119. Relay 116 remains operated by the current flowthroughits'upper winding alone.v Relay 119 however, fallsbackfshuritgfthe associated condensers, and would remove the shunt fromaround the up per winding of relay 115 were it not forthe upper'contactso f relay 115 which closes a multiple pointin itsown shunt circuit. Theringing current now passes out over the up-. per conductor. 120 to theswitch train and causes the: automatic signalling of the calledsubscriber to start in a manner explained in the /Vicks patentherein'before referred to.

When the operator restores the ringing key,'the ringing current isremoved and the resistance llisshort circuited. Whenthis occurs, thesupervisory. lamp 112'is1again lighted, and relay 115 v again pulls up."The ground potential placed on. conductor 121; during the time thatrelay 115is'deenergized with relay 1-16 operated is effective inmaintaining operated the-line -relay*which has a windingv connectedbetween battery and c' n-- ductor 121 at this time} I Whenthe calledsubscriber responds,; tlie 5 talking circuit is closed in theswitohftrain andthe current flow over con'ductors'120'and 121 isstopped, the so called dry trunksupervision-being used, Whenthis'occurs, relay 119 falls back and short circuits the assooiat-'edlgcondensersin the talking;circuit so as to afliord abetter talkingcondition and removes then bridge through--res stance 118' irom'acrossthe talking circuit. -At the sarne time,

relay119 removesthe shunt from around the ,upperwinding of relay 116,thereby extinguishing the supervisory lamp 112, which I I does notremain lighted in series" with the entire winding of the sleeve relay.

resumed, operatingl'relay- 119 to again re place the shunt around theupper winding of thesleeve relay, giving a disconnect sign ah Thedistant operator'may-senda disconnect-rapplication of ringing'currentover the toll line,v in whichicase relay "1077' of the cord circuitoperates and 1 removes the shunt from around. relay 106,:whe'reuponrelay 106 operates' and opens a further point in itsshunt circuit, atthe: same time closinga circuit for the lamp 103,-which lamp becomeslighted a disconnect signal; :Q

- When the operator pulls "down the connection;the-bord-circuit'apparatus reverts to its v position, and the-tollservice switch normaltran i11s released. Assuming now that the operator desires to collect acoin deposited-at apay' station callediover the cord circuit shown inthe I drawings andiover the tQll serVicetrunk rshown, sheoperates -hercollect call key I ,with the talking key thrown the, cord; This ofcourse takes place after the (con 'nection has been setup "to the line,in

' which-case the ele'ctro pola-rized"relay 116 is: operated; :When the:collect" call key is thrown, the ;lower contactsof the keyf operatevrelay 20t which= splits the cord and places i the current i from I, thenegative 110 volt' source'on the extended tip""conductor 134.-' Theoperated key also removes battery from the extended sleeve conductor136, deenergizing isleeve relay 115'.v 1 Sleeve relay 7 115 opensthe-circuit'throughrelayf119,"deenergizing this relay sons to shunt thecon-:-

Ideterrnined interval or takes such other steps I densersand permit thehigh voltagejcurrent to pass overtheupper conductor 120. Be lay115also-clo'ses a groundreturn' circuit at its lowercontact to conductor121 so as; to afiord a return path'for the-highlvoltage- I current undercertainiconditionsfofthe switch lay 109 to close" whereupon the supervitrainarid-0 aroma "taming circuit for the In the same way, the operatormay refund I a coin-,- by-operating "therefund*call key automaticswitches. yWlien "the rel 1 stored, the" circuits shown return to'their" previous condition.

In"' case 'theioperat'or desires to'iconverse over the answering end of*the cord gwnne; the calling end isfcutofi, she operates thec'utfj 'oficall key, operating relay204 to cut'bfi the' calling end, leaving her"headset connected-"- to the answering end er the cord.

It Will be' noted that the keys above referred vto' appear, in duplicateon both ends of the, common equipment so that either end ofthe cord may"be usedQin efieeting a connection; It is to be noted"especiallythat, theend of the cord over which 'diallingjirn f" pulses are transmitted isdependent entire ly'upon whichof the two, dial keysisfthrown when thedial moves fromits 'normarp'esig tio'n-g- If the dial call key is thrownas -hl' -e ;--inbefore described, the answering'cut-bff te lay?"20'l"isoperated as hereinbefore pointed stead, the calling cut-foff anyxeor 'isoperate'd' instead, and the dialypulses areitransJ- fl mit'ted over theanswering end of [the cord;

Assuming'now that thejoperator 'WiShBS tof "time a connection andtobe'notified wlien.,f*-'

a 'c'onversation has proceeded "ffor a prede terininedf length of: time,for example, three minutes, she operates the 'fcoinmonpush'f button PB,Fig. 1, while the talking key and";

corresponding 'relay l 08' ,of the cord "circuit i'o riv h hefq n' f ten is pass 'giar operated? ,Wlien'u' this occurs,- a c cuitfisclosedsfor' the starting; relay ll :1, f whereupon i i this relayoperates and lock fitselfi f to the sleeve conductor in multiple withthe su ervisory ;lamp,"at the fsaine time i'openin'g its initial circuitand preparing a j'c'ircuit'forfth i when retarded relay 109, which iscomp tard'ed by asu'itable slow-acting device,"such the' predetermined'intervalfithe s19 actlng device tll'Offlaerrni-ts thecontactsf ofa v, r:Y. lamp *112 commences to flash und'ergth'ef Goa; tI'OlTOf the flasher'F'. The resistancdas'so ciatefd'withi-theflasherF in the flashinglead'whichthe" plug 1?? is inserted. i

subscribers that they have conversedlthe preas she-may be: instructed:totake;

is toffprevent the short 'cirouiting "of the sleeve relay" associated'With'the" jack? in'td 7 T 3 f.

i p i 'q 1, 7 fl l l f fibf e" I su ri y f ainpi .1 2, the bp' r'a br?-L." operates her talking key andniaywai'n ih6' W hen the operatorthrowsher i h 2 8 ali 11 em ns pf s ii b relayf'lf'OQTis thereuponreleased tostop the'fif "flashing operatioiii Elf-the" subscribers have"7 V the conductors of said trunk line connectedv to the outgoing sideof said-condenser, a seca desire to converse for another period of time,the operator merely restores her talking key, whereupon thetimingoperation commences agam.

' What is claimed is:

1. Ina telephonesystem, a trunk line including two talking conductors, abridge across'said talking conductors, a relay energized responsive tocurrent flow through said bridge, a second bridge, a condenser'connectedin series withone talking conductor and directly shunted when said relayis normal, and contacts on said relay effective when the relay isoperated to remove the shunt from around said condenser and to placesaid second bridge directly in multiple with the first.

2. In a telephone system, a'trunk line including two talking,conductors, acondenser in series with one of said talking conductors, abridge across said talking conductors on one side of said condenser, arelay in said bridge responsive'toticurrent fiow over said trunk line, ashunt'aroundsaid condenser controlled by saidirelay, a'second bridgeacross said trunk line in multiple with the first bridge when the relayiseoperated, and

contacts onv said relay for opening the second bridge and for shuntingsaid condenser when the'relay falls back responsive. to a cessation I incurrent flow over said trunk line.

3. Ina telephone system, a trunk line comprising two, talking conductorsoutgoing from a switchboard, a condenser inserted in one of saidtalkingconductors, a shunt normally around'said condenser, a bridge across 011dbridge across sai'dtrunk line directly in multiple with the firstbridge, inean'sfforplacing a bridge across the trunk line on theswitchboard side of said condenser and for opening the first namedbridge, means responsiveto the cessationbf current flow in the firstnamed "bridge for 'shuting said condenser and forlremoving the secondbridge from across the trunkline. v I

4. In a telephone system, atrunk line, three bridges arranged to beplaced across said trunk line, means for, placing the first bridgeacross the said trunk line, means responsive to the resulting currentflow through the first bridge for placing the second bridge across thetrunk line, means'for preparing the third;

bridge and for opening the first bridge, means responsive to theresulting cessation of current flow inthefirst bridge for reniov ing thesecond bridge from across the trunk lineand for placing the third bridgeacross the trunkline. i

55111 a telephone system, a bridges arranged to be placedacross saidtrunk line, means for placing the first bridge across the trunkline,'means for preparing the second" bridge 'and ..for opening. thefirst bridge,mean s responsive to the opening of trunk line, two

holding bridge is opened to permit the condenserstobe shunted for the 6.In a telephone system, a trunk line extending from a manual switchboardto an automatic switchboard, means for extending a connection to saidtrunk line at said manual switchboard and for placing a switch holdingbridge across the trunk line, said bridge,

excluding said manual switchboard, operator-controlled means for openingsaid holdmg bridge to permit the. operation of the mechanism at theautomatic switchboard to I be controlled from the manual switchboard andfor opening it subsequently to permit ringing current to be transmittedfrom the manual switchboard to the automatic switch board, a device atsaid'manual switchboard end of said trunk revertively controlled from,the automatic switchboard after the automatic switching mechanism hasbeen set and before the ringing current has been transmitted, and meanscontrolled by said: device for rendering effective an, alternativeholding circuit for the automatic switching mechanism when said bridgeis opened to permit the passage of ringing current.

7. Ina telephone system, a trunk line ex tending from a manualswitchboard to an au tomaticswitchboard, ringin'g-current-block ingcondensers inserted in said trunk line, means controlled by the operatorat said manual switchboard for shunting said condensers to permit themechanism at the aui V tomatic switchboard to be controlled from themanual switchboard and for subsequently shunting? the condenserstopermit the pas- ;sage of ringing current, a holding bridge 9 acrosssaid trunk 11116 on the automatic switchboardside'ofsaid condensers, thesaid condenser shunting means being rendered cf- 7 festive upon acessation of the'ocurrent fiowT in said holding bridge, analternative'switch holding circuit path, and means revertivelycontrolledfrom the automatic switchboard."

after the connection has been set up andbe fore the ringing currenthasbeentransmit- 1 ted for preparing said alternativexswitchr holding pathso that it is completed when the a bridge across said trunk line at themanual switchboard end, a polarized relay included in said bridge,-and asWitch-holding circuit path alternative to said bridge and controlled 7by said relay.

49. In a telephone system,atrunkqline extending from a manualswitchboard to an automatic switchboard whereat a current flow in agiven direction is brought about over. said trunk line while: aconnection is being set up through the automatic switchboard and areversed current flow is caused to take place after the connection issetup and before and after conversation, and whereat the current flow overthe trunk line is prevented during conversation, a bridge across saidtrunk line at the manual switchboard end'thereof including a polarizedand a non-polarized relay, a supervisory lamp, and a circuit for saidlamp controlled by said relays jointly.

10. In a combined manualand automatic telephone system in whichautomatic switches may be operated from a manualswitchboard, a linkcircuit at said manual switchboard comprising two sections, a callingdevice for controlling the operation of automaticswitohes, said callingdevice having anormal position, and meansresponsiveto the movement ofsaid calling device from its normal position to effect the control ofsaid switches for associatingsaid calling device with one section ofsaid link circuit to'the exclusion oi the other and foricancelling suchassociation upon the return of the calling device to normal.

11. In a combined manual and automatic:

ing device for controlling the operation of r automatic switches overelther sectlon of said link circult, a key contact forpredetermlning theassociation. of said calling device with either of said sections, andmeans effective upon the turning of the call ng devlce oil normal forcompleting the predetermined association. I p v 13. In a;telephonesystem, an operators link circuit comprising two sections, a callingdevice for association with either section,op erator controlledrmeansfor predeterminingwith which section the calling device shall beassociated to the exclusion of theother and means eii'ective upon'themanipulation of said calling device bythe operator for carrying intoeffect the predetermined operation,

14. In a telephone system, an operators link circuit divided into threesections, a call- 1 ing'device connected to the middle section, av

relay associatedwith the first section for disconnecting the firstsection from the middle section to permit'the'calling device to'operajte over the middle and' third sections, [a second" relaysiinilarlyassociatediwith the first sec tion; coin on oliapparatus, and means foroo'eratin ithei of and, rcla s selectivel 1 l D i when 'saidcoincontrolled apparatus is being idjvhjen'said calling device is being" 15,In a telephone system, an operatoi"s link circuit dividil 1 into threesections, arelayffor di onnecting the middlesection from the; firstsection, a slinilar relay for disconnecting f theiniddleisection fromtheo'third section, a

callingdelice connected to the middle section, means for operatingelther of said relays whenthe-calling device is in use, and means for,operating eitherof said relays-selectively when saidc'alling deviceisnot in use 1 6. In atelephone system inwhich connectionsfaresetupthrough link circuitsjat'a "33" manualswitchboard, a separatetiming device for e chiink circuit, and operator-controlled,

means 'co-mmonftoall link circuits for, ng anydes red tlmlngdevice.

1' Zl Ina tel phone system, atrunk line eXQ tending fromja manualswitchboard, a bridge across said trunk line at the, manual switchboardincluding a polarized'fr elay and a nony i i tlr r a o 18." n1atelephonesystenna trunk line eX- tending from a manual switchboard, abridge across'said trunklineat the manual switch board including apolarized relay and a nonpolarized relay, a supervisory device, contactson: each relay, and a circuit for said device including said contacts inseries. I

- 19. In a telephone systemin which'connections are set up throughlink'circuitsvat a manual switchboard, a separate timing device mon toallsaid timing devices,'means for associating said starting device'withany one of said timing devices, and means responsive to, I a subsequentoperation of the starting device torstarting the associated timingdevice.

20. In a telephone system in which connections are set i up through linkcircuits at fa manual switchboard aseparatetiming device f I,

for each link circuit, a talking key for each link circuit operableunder the control'of the operator at the switch-board,'a starting devicecommon to all-said timing devices, and means responsive to an operationof said starting for each link circuit,a starting device comdevice forstarting the operation of the timdevice associated with any link circuitat which the talking key is operated. I

'21. Ina'telephone system, a link circuit comprisin'g'two sections, acalling device normally connected to'both sections,means"forselectingeither section, and means automatically responsive to an'operation'rof the polariz'edfrelay," a supervisory; device, and a n 957 Y Y circuit 'for said device controlled by said calling device fordisconnecting the calling device from the other section.

22. In a telephone system, a link'circuit comprising two sections, acalling device normally associated with both sections, means forselecting either section, and means automatically responsive to anoperation of the calling device for disassociating the calling devicefrom the other section.

23. In a telephone system a plurality of individual link circuits eachcomprising two sections, a common link circuit comprising two sectionsand containing a calling device arranged to exercise a control overswitching apparatus by way of either section of any individual linkcircuit, means for connecting the sections of said common link circuitto the sections, respectively, of any individual link circuit and forselecting either section of the common link circuit, and meansautomatically responsive to anoperation of said calling device toexercise a control over switching apparatus by way of the selectedsection of the common link and the connected section of the individuallink for disassociating said calling device from the other section ofthe common link and connected section oi the individual link.

In witness whereof, I hereunto subscribe my name this 24th day ofSeptember, A. D.

THOMAS F. CROCKER.

